This invention relates generally to apparatus for providing instant hot water at remotely located hot water faucets within residential and small commercial buildings and, more particularly to an inexpensive, yet reliable, hot water circulation apparatus that maintains hot water at such remote faucets through natural convective circulation flow from the existing building water heater.
Considerable time and water are wasted daily while consumers await hot water at faucets remotely located from the building water heater. In some plumbing installations, this delay may be up to two minutes, which results in wasting up to 8,000 liters of water annually in the average home, to say nothing of the attendant frustration. Many attempts at resolving this problem have been made. One such attempt has been the installation of auxiliary remote water heaters, either under sinks in proximity to the remote faucet or in a basement located beneath the sink above. Another such attempt at providing instant hot water at remote faucets has involved bringing heated water from the existing water heater to the faucet via the existing hot water pipe serving that faucet and circulating it back to the water heater through a separate return line.
Exemplary of systems employing auxiliary water heaters is that described in U.S. Pat. No. 4,236,548 to Howard. However, initial purchase and installation costs of auxiliary water heaters has limited their acceptance. In addition, they consume valuable under-counter space if located near the remote faucet. Some auxiliary heaters are intended to provide limited quantities of very hot water at a faucet that is entirely separate from the usual hot water faucet for the specialized purpose of providing very hot water for instant soups and beverages. These specialized auxiliary water heaters are unrelated to the present invention.
Water circulation systems are generally grouped as either convective or pumped circulation systems. Exemplary of convective circulation systems are those described in U.S. Pat. No. 3,929,153 to Hasty and U.S. Pat. No. 2,255,460 to Weaver. These systems employ water supply pipes to the remote faucet that are positioned to slope upwardly and return lines from the faucet back to the water heater inlet that are positioned to slope downwardly. Such systems are difficult to implement, especially in existing buildings. Many of these systems, as recognized by Hasty, also suffer the disadvantage of some water in the cold water pipe being mixed with hot return line water, which then must be wasted if cold water is desired at a cold water faucet. Heating of the cold water is a common problem in circulation systems, and many installations do not lend themselves to the replumbing that is required to minimize this problem.
Pumps employed in recirculation systems, such as those described in U.S. Pat. No. 3,669,351 to Meier and U.S. Pat. No. 4,142,515 to Skaats are functional, but require electrical power that may not be readily available in the desired location. These systems are very complex, requiring motors, seals, switches, timers, control electronics, and electrical wiring for proper operation. These components are not only expensive, but they are subject to failure. Operational costs to operate the pump will be incurred, and a pump may produce noise that could be objectionable to some people. The Skaats patent also recognizes the undesirable tendency of some water circulation systems to heat the cold water in the cold water distribution pipe by the warm water from the return water line.
While the aspirator activated hot water circulation systems described by the present inventor in his U.S. Pat. No. 5,331,996 and U.S. Pat. No. 5,518,022 will perform well in all situations, whether or not convective flow is possible, or where only a small return line can be installed, the present invention will operate in a significant percentage of domestic applications in which the water heater is in the basement and the remote hot water faucet is on the first or a higher floor, or in which the remote hot water faucet is a minumum of one meter above the water heater.
The present invention provides an integral water circulation apparatus for supplying instant hot water at hot water faucets remotely located from the building water heater through a convective circulation flow of hot water from the water heater. It is therefore simpler in design, less expensive to install and more reliable than the more complex prior art systems. It has the further advantages of not mixing heated return line water with cold water being supplied to cold water faucets throughout the building and of preventing cold water from flowing up the return line to the hot water faucet